<!DOCTYPE html>
<html lang="en">
	<head>
	<title>three.js - BufferGeometry selectively drawn using attributes and a shader</title>
	<meta charset="utf-8">
	<meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">
	<style>
		body {
			background-color: #000;
			font-family: Monospace;
			margin: 0;
			color: #000;
			overflow: hidden;
		}
		a {
			color:#ff0;
		}
		#title {
			position: absolute;
			width: 100%;
			top: 0;
			height: 20px;
			padding: 0;
			text-align: center;
			font-size: 1.1em;
			background-color: rgba(64,96,64,0.7);
			color: #fff;
		}
        #ui {
        	position:absolute;
        	left:0;
        	top: 20px;
        	padding: 0;
        	text-align: center;
        	width:100%;
        	height:20px;
        	color: #fff;
        	background-color: rgba(64,96,64,0.6);
		}
	</style>
	<script type="text/javascript" src="../build/three.js"></script>
	<script type="text/javascript" src="js/Detector.js"></script>
	<script type="text/javascript" src="js/libs/stats.min.js"></script>

	<script type="x-shader/x-vertex" id="vertexshader">
		attribute float visible;
		varying float vVisible;
		attribute vec3 vertColor;
		varying vec3 vColor;

		void main() {
			vColor = vertColor;
			vVisible = visible;
			gl_Position = projectionMatrix * modelViewMatrix * vec4(position,1.0);
		}
	</script>
	<script type="x-shader/x-fragment" id="fragmentshader">
		varying float vVisible;
		varying vec3 vColor;

		void main() {
			if ( vVisible > 0.0 ) {
				gl_FragColor = vec4( vColor, 1.0 );
			} else {
				discard;
			}
		}
	</script>
	</head>
	<body onload="app()">
		<div id="title"></div>
		<div id="ui"><a href="#" onclick="hideLines();">CULL SOME LINES</a> - <a href="#" onclick="showAllLines();">SHOW ALL LINES</a></div>
		<script>
		var camera, scene, renderer, stats;
		var geometry, mesh;
		var numLat = 100;
		var numLng = 200;
		var numLinesCulled = 0;

		function app() {

			if ( ! Detector.webgl ) {

				Detector.addGetWebGLMessage();

			}

			init();
			animate();

		}

		function init() {

			renderer = new THREE.WebGLRenderer( {
				antialias: true
			} );
			renderer.setClearColor( 0x000000, 0.0 );
			renderer.setPixelRatio( window.devicePixelRatio );
			renderer.setSize( window.innerWidth, window.innerHeight );

			document.body.appendChild( renderer.domElement );

			scene = new THREE.Scene();

			camera = new THREE.PerspectiveCamera( 45, window.innerWidth / window.innerHeight, 0.01, 10 );
			camera.position.z = 3.5;

			scene.add( new THREE.AmbientLight( 0x444444 ) );

			stats = new Stats();
			document.body.appendChild( stats.dom );

			window.addEventListener( 'resize', onWindowResize, false );

			addLines( 1.0 );

		}

		function addLines( radius ) {

			geometry = new THREE.BufferGeometry();
			var linePositions = new Float32Array( numLat * numLng * 3 * 2 );
			var lineColors = new Float32Array( numLat * numLng * 3 * 2 );
			var visible = new Float32Array( numLat * numLng * 2 );

			for ( var i = 0; i < numLat; ++ i ) {

				for ( var j = 0; j < numLng; ++ j ) {

					var lat = ( Math.random() * Math.PI ) / 50.0 + i / numLat * Math.PI;
					var lng = ( Math.random() * Math.PI ) / 50.0 + j / numLng * 2 * Math.PI;

					var index = i * numLng + j;

					linePositions[ index * 6 + 0 ] = 0;
					linePositions[ index * 6 + 1 ] = 0;
					linePositions[ index * 6 + 2 ] = 0;
					linePositions[ index * 6 + 3 ] = radius * Math.sin( lat ) * Math.cos( lng );
					linePositions[ index * 6 + 4 ] = radius * Math.cos( lat );
					linePositions[ index * 6 + 5 ] = radius * Math.sin( lat ) * Math.sin( lng );

					var color = new THREE.Color( 0xffffff );

					color.setHSL( lat / Math.PI, 1.0, 0.2 );
					lineColors[ index * 6 + 0 ] = color.r;
					lineColors[ index * 6 + 1 ] = color.g;
					lineColors[ index * 6 + 2 ] = color.b;

					color.setHSL( lat / Math.PI, 1.0, 0.7 );
					lineColors[ index * 6 + 3 ] = color.r;
					lineColors[ index * 6 + 4 ] = color.g;
					lineColors[ index * 6 + 5 ] = color.b;

					// non-0 is visible
					visible[ index * 2 + 0 ] = 1.0;
					visible[ index * 2 + 1 ] = 1.0;

				}

			}

			geometry.addAttribute( 'position', new THREE.BufferAttribute( linePositions, 3 ) );
			geometry.addAttribute( 'vertColor', new THREE.BufferAttribute( lineColors, 3 ) );
			geometry.addAttribute( 'visible', new THREE.BufferAttribute( visible, 1 ) );

			geometry.computeBoundingSphere();

			var shaderMaterial = new THREE.ShaderMaterial( {

				vertexShader: document.getElementById( 'vertexshader' ).textContent,
				fragmentShader: document.getElementById( 'fragmentshader' ).textContent
			} );

			mesh = new THREE.LineSegments( geometry, shaderMaterial );
			scene.add( mesh );

			updateCount();

		}

		function updateCount() {

			var str = 'BufferGeometry selective drawing: 1 draw call, ' + numLat * numLng + ' lines, ' + numLinesCulled + ' culled (<a target="_blank" href="http://callum.com">author</a>)';
			document.getElementById( 'title' ).innerHTML = str.replace( /\B(?=(\d{3})+(?!\d))/g, "," );
		}

		function hideLines() {

			for ( var i = 0; i < geometry.attributes.visible.array.length; i += 2 ) {

				if ( Math.random() > 0.75 ) {

					if ( geometry.attributes.visible.array[ i + 0 ] ) {

						++ numLinesCulled;

					}

					geometry.attributes.visible.array[ i + 0 ] = 0;
					geometry.attributes.visible.array[ i + 1 ] = 0;

				}

			}
			geometry.attributes.visible.needsUpdate = true;

			updateCount();

		}

		function showAllLines() {

			numLinesCulled = 0;

			for ( var i = 0; i < geometry.attributes.visible.array.length; i += 2 ) {

				geometry.attributes.visible.array[ i + 0 ] = 1;
				geometry.attributes.visible.array[ i + 1 ] = 1;

			}

			geometry.attributes.visible.needsUpdate = true;

			updateCount();

		}

		function onWindowResize() {

			camera.aspect = window.innerWidth / window.innerHeight;
			camera.updateProjectionMatrix();
			renderer.setSize( window.innerWidth, window.innerHeight );

		}

		function animate( time ) {

			requestAnimationFrame( animate );

			var time = Date.now() * 0.001;

			mesh.rotation.x = time * 0.25;
			mesh.rotation.y = time * 0.5;

			stats.update();
			renderer.render( scene, camera );

		}

		</script>
	</body>
</html>
